The present invention relates to a jolt control system in a motor vehicle, and more particularly to jolt control in a motor vehicle drive system including an internal combustion engine and an automatic transmission that is variable in steps.
Jolt control systems are known in which the torque delivered by the internal combustion engine is decreased during the gear shift operation. For example, in U.S. Pat. No. 4,266,447 (Hess et al.), a jolt control system is described in which the engine torque is decreased during a gear shift from the time the engine speed reaches an initiating speed until the time the engine speed reaches an end speed. Various different initiating and end speeds are stored in a plurality of storage locations in storage. Addresses in the storage are computed in response to the engine speed signal and upshift or downshift signal for calling out the initiating speed and end speed from the storage.
U.S. Pat. No. 4,355,550 (Will et al.) discloses a jolt control system wherein the torque delivered from the internal combustion engine is decreased during a gear shift at a gradual changing rate.
U.S. Pat. No. 4,403,527 (Mohl et al.) discloses a jolt control system. An automatic transmission control unit in a motor vehicle furnishes a signal which signifies that the torque delivered by the internal combustion engine is to be decreased. In response to this signal, the ignition timing is delayed or the width of fuel injection pulses is shortened.
JP 58-77138 A (Toyota) discloses a jolt control system. In this known system, the torque delivered from the internal combustion engine is decreased during a gear shift with the engine throttle kept opened, while the torque is increased during a downshift caused by deceleration with the engine throttle held at idle speed position.
These known jolt control systems have the common disadvantage that the torque delivered by the internal combustion engine is either decreased or increased during a gear shift. None of these systems consider that the torque delivered by the internal combustion engine should be increased and then decreased in order to suppress undesired variation in the torque delivered by the transmission output shaft during a gear shift. For example, during an upshift, the torque delivered by the transmission output shaft is decreased during the torque phase and then increased during the subsequent inertia phase. During a downshift, the torque delivered by the transmission output shaft is decreased during the inertia phase and then increased at the end of the downshift.
An object of the present invention is to provide a jolt control system which is improved such that the torque delivered by the internal combustion engine is varied in the optimum manner so as to suppress undesired variation in the torque delivered by the transmission output shaft during a gear shift.